1. Field of Invention
The present invention relates to a scanner. More particularly, the present invention relates to scanning circuit structure.
2. Description of Related Art
In recent years, rapid progress in digital technologies has lead to the development of Internet and multimedia systems. Accompanying this trend, a large number of analog images are routinely converted into a digital format to facilitate processing. A digital camera (DC) is used to extract an image from an actual scene. Similarly, an optical scanner is used to extract textual data from a document or image data from a picture. The extracted data is converted into a digital format so that a computer or electronic equipment may display an image, carry out an optical character recognition, edit the data, store up the data or simply output to some devices.
According to the method of inputting document image, optical scanners may be classified as a palmtop scanner, a sheet feed scanner, a drum scanner or a flatbed scanner. FIG. 1 is a diagram showing the circuit structure of a conventional scanner. As shown in FIG. 1, the circuit includes an optical sensor circuit module 120 and a main circuit module 110. Each circuit module is fabricated on a printed circuit board. The circuit modules 110 and 120 communicate with each other through a flat cable 130. In general, the main circuit module 110 is fixed inside the lower casing of a scanner while the optical sensor circuit module 120 is attached to a scanning module capable of moving longitudinally. The optical sensor circuit module 120 has a charge-coupled device 140 therein. The charge-coupled device 140 can sense the light reflected from the image within a scan document to produce analog image signals. The analog image signals are transmitted to the main circuit module 120 by a form of analog voltage signals through the flat cable 130. The main circuit module 120 processes the analog image signals and converts the analog image signals into digital image data, so as to provide a user to retrieve the digital image data file to carry out various operations including image display, optical character recognition, editing, data archiving or data transfer through a computer or other electronic device. In addition, to capture the image produced by the reflected light while scanning the document, the charge-coupled device 140 must receive timing control signals from the main circuit module 120 as well. Hence, the flat cable 130 must carry both timing control signals and analog image signals.
When demand for image quality is low, a flat cable is adequate because the quantity of image data that needs to be transferred is small. However, due to rapid expansion of computer power, the production of a high-quality scan image at a shorter scan period is always in demand. Eventually, to meet these demands, the flat cable has to carry greater quantities of analog image signals and timing control signals. In other words, the flat cable not only has to transmit signal at a higher rate, but also has to increase the number of transmission lines for transmitting timing control signals. The additional transmission lines for carrying control signals may cause electromagnetic interference (EMI) of analog image signals. Ultimately, image data may be distorted.